1. Field of the Invention
The present invention relates to an electron emission device, and more particularly to such a device having an electron emission electrode with a pointed end and an electrode positioned opposite to said pointed end.
2. Related Background Art
As an electron source there has been utilized thermal electron emission from a thermal cathode. Such an electron emission utilizing thermal cathode has been associated with the drawbacks of a large energy loss in heating, necessity of heating means, a considerable time required for preparatory heating, and the tendency of instability of the system caused by heat.
For these reasons there have been developed electron emission devices not relying on heating, among which there is known an electron emission device of field effect (FE) type.
FIG. 1 is a schematic view of a conventional electron emission device of field effect type.
As shown in FIG. 1, the conventional electron emission device of field effect type is composed of a cathode chip 20 formed on a substrate 23 and having a sharply pointed end for obtaining a strong electric field, and an attracting electrode 22 formed on the substrate 23 across an insulating layer 21 and having an approximately circular aperture around the pointed end of the cathode chip 20, wherein a voltage is applied across said cathode chip 20 and said attracting electrode 22 with the positive side at the latter, thereby causing electron emission from the pointed end of the cathode chip 20 where the intensity of electric field is larger.
However, in such a conventional field effect electron emission device, the sharp pointed end of the cathode chip 20 is difficult to make, and has been generally manufactured by electrolytic polishing followed by remolding. This process is however cumbersome, requiring many working steps, and is difficult to automate as it involves various empirical factors. Consequently the manufacturing conditions fluctuate easily, and the product quality cannot be made constant. Also the laminate structure tends to result in a registration error between the cathode chip 20 and the attracting electrode 22.